How to find a Docker container's ID, filtering by the container's name

I know this should probably be common knowledge, but I always want to find a way to do this, and always find it, and then forget it, and the cycle continues.

So, if you want to find a running Docker image named bootifulmongo, and get its container ID as the output, then run:

docker ps -aqf name=bootifulmongo

You could of course very usefully script its execution by storing the output as a variable:

CONTAINER_ID=`docker ps -aqf name=bootifulmongo`
echo "the container ID is ${CONTAINER_ID}."